Ceramic burners

ABSTRACT

A ceramic burner for hot blast stoves for blast furnaces. A ceramic block has a central hole and a crown of holes surrounding it. A vertical conduit feeds gaseous fie; and a second coaxial conduit supplies combustion air. The conduits have their upper ends passing through the holes. The upper surface of the block slants upwardly from the central hole and the holes of said crown are directed toward the prolonged axis of the central hole. The central hole has essentially the shape of a rectangular slot and the sloping part of the upper surface of the block comprising essentially two flat surfaces which comprise an angle of 40*120*, and the crown of holes is subdivided into two rows of holes running parallel to each other and to the longitudinal sides of said central hole. The rectangular shape of the central hole shows a ratio of length versus width between 4:1 and 6:1 and the slot width is less than 600 mm. Each of the two rows of holes has at least four holes the middle axis of which form together with the prolongation of the axis of the central hole an angle ranging from 20* to 70*.

United States Patent [54] CERAMIC BURNERS [5 6] References Cited UNlTEDSTATES PATENTS 2,437,042 3/1948. Prosser et a1. 239/430X A [72] Inventrs Ja lls Bll 3,185,458 5/1965 Reed 431/190X Santpoort;

Primary Examiner-Carroll B. Dority, Jr. $222: ouwerkerk hmmdenAttomey-Wenderoth, Lind and Ponack [21] Appl. No. 867,988 [22] FiledOct. 17, 1969 4 i g z A G ABSTRACT: A ceramic burner for hot blaststoves for blast s e b d Ge furnaces. A ceramic block has a centralholeand a crown of 32} P :3 many holes surrounding it. A vertical conduitfeeds gaseous tie; and nonty a second coaxial conduit suppliescombustion air. The cong P 733 4 duits have their upper ends passingthrough the holes'. The

upper surface of the block slants upwardly from the central hole and theholes of said crown are directed toward the prolonged axis of thecentral hole. The'central hole has essentially the shape of arectangular slot and the sloping part of the upper surface of the blockcomprising essentially two flat surfaces which comprise an angle of 40 120, and the crown of holes is subidvided into two rows of holes runningparallel to each other and to the longitudinal sides of said centralhole. The rectangular shape of the central hole shows a ratio of lengthversus width between 4:1 and 6:1 and the slot width is less than 600 mm.Each of the two rows of holes has at least four holes the middle axis ofwhich form together with the prolongation of the axis of the centralhole an angle ranging from CERAMIC BURNERS The invention refers to aceramic burner, particularly to be used in .hot blast stoves for blastfurnaces comprising a first vertical conduit for the feeding of gaseouscombustible fuel and a second coaxial conduit for the feeding ofcombustion air, whereby the conduits on their upper ends pass into aceramic block through perforations, namely into a central hole with acrown of holes around it, whereby the upper surface of the block runsinclined from the central hole upwards and theholes of the crown aredirected towards the prolonged axis of the central hole.

Ceramic burners of the types mentioned above are presently commonconstruction elements in hot blast stoves for blast furnaces. Theyconstitute a process as compared to the formeily common metal burnerswhich were installed outside the combustion chamber of the hot blaststove. With the ceramic burner being built into the hot blast stove aconsiderably higher cupola temperature can be attained, without theburner suffering any damage by it. Moreover it is possible to avoid,through a ceramic burner installed vertically inside a combustionchamber the rebounding of the flames on the separation wall between thecombustion chamber and the lattice work, particularly inthe place wherethe difference of temperature between the combustion chamber and thelattice work should be the highest. Thus the separation wall and thelattice work are both greatly spared.

The known ceramic burners have a round or oval-shaped exit opening atthe (central hole for the fuel supply. The holes of the surroundingcrown are slot'shaped and equal in size. Although the known ceramicburners represent a considerable improvement over the older metalburnersthey can still be improved. On top of the cupola and under thelattice work of the hot blast stove an important amount of unburnedgases can be measured, mainly CO and this notwithstanding the fact thata sufficient supply of combustion air has been provided. Even at this,the economy of the installation is not yet optimal. Also the combustionis uneven, particularly in the lower part of the combustion chamber. Anobject of the present invention is to eliminate these imperfections.

A further object is to secure a better control and mixing of the fueland air up until it arrives into the flame thereby influencing theevenness and completeness of the combustion.

A further object is to provide a construction wherein the central holeessentially has the shape of a rectangular slot with the sloping part ofthe upper surface'of the block composed essentially of two flat surfacesmaking an angle of -l20 and preferably 60-90 and having the crown ofholes subdivided into two rows of holes parallel to each other and tothe sides of the central hole.

Several devices have been used with metal burners in order to improvethe mixing of gas and air. These known constructions cannot be used forceramic burners for hot blast stoves, due to their dimensions as well asto the restricted construction possibilities with ceramic stones,whereby the oval shape of the combustion chamber poses specificconstruction conditions to the expert.

Even though greater successes have been achieved with any shape of holesin the ceramic block, it has been proven that the rectangular shape ofthe central hole according to the invention is particularlyadvantageous, whereby preferably the relationship of length and widthshould be between 4:1 and 6:1 and the slot width of the hole less than600 mm.

Besides it has proven to be advantageous to provide the two rows with atleast four holes, whereby their middle axes together with the extensionof the axis of the central hole form an angle of 20 to 70.

The advantageous effect of the new burner should be attributed to thevery intensive mixing of air and fuel, which because of this shape ofthe burner can be achieved. The air jets which penetrate the relativelynarrow jet of fuel and specifically adapted shape of the upper surfaceof the block prevent the possibility that fuel and air jets that areunmixed,

or incompletely mixed or mixed in the wrong proportion persist untilthey reach the flame. It may be assumed, that in the case of the known,coaxial distribution of the air holes around a central circular hole forthe introduction of fuel the air mixing ratio over the burner shows agradient. Therefore theoretically only within a relatively narrow zoneof the mixing area good mixing conditions may be expected in the knownceramic burners. a

An object of the invention is also the specific distribution of theholes of both rows to each other. The expert would consider it useful,in order to improve the mixture of gas and air, that the different holesare distributed at different heights. To be sure such a distribution isalso covered by the invention, but surprisingly enough, in the burneraccording to the inven tion better results have been obtained when theholes on both rows are distributed on the same height.

According to the purpose and/or circumstances of utilization it may beadvantageous accordingto the invention to distribute every two holes ofthe two rows across each other or the holes of one row staggered inrelation to the other row. The best shaping effect of the ceramic blockis obtained, when the distribution of the fuel and the air over thecross section of the central hole, and/or over the different holes isdistributed as evenly as possible. In order to promote the evennness ofthe distribution the two conduits should join shortly before passingover to the holes through the ceramic block. 7

Further objects of the invention and their advantages will beillustrated in the drawings, which represent a schematic form ofconstruction according to the invention, in which:

FIG. 1 shows schematically a hot blast stove with a built in burner in alongitudinal section;

FIG. 2 shows the burner of FIG. 1 at an enlarged scale;

FIG. 3 is a section according to line lII-III in FlG. 2.

In FIG. 1 the housing of a hot blast stove is designated by l and 2 isthe bottom on which it stands, forming together a brick entity. Thebrick housing is surrounded by a steel casing (not shown). A number ofpillars 3 projecting out of the bottom 2 support a lattice 4, which inturn serves for supporting the perforated stones piled up on it (notshown) through which is led alternately hot fuel gas from the top downand air to be heated from the bottom upwardsQThis so-called lattice workconstruction is separated by a wall 5 from the combustion chamber, whichtowards the outside is limited by a section of the housing 1. The hotblast stove is shut off on the top by a brick cupola 6 and a steelcupola 7.

The gaseous fuel material necessary for the conservation of the hot fuelgases and the air are led through a conduit 8 and/or a ring conduit 9 tothe combustion block 10. The burner is indicated only schematically inFIG. 1. Above the burner the fuel material and the air are intimatelymixed and the fuel material is burned inxthe combustion chamber.

The hot combustion gases are led over the separation wall 5. Once thepiled up stones over the lattice work are conveniently heated, the feedopenings 14 and 15 of the combustion and air conduits 8 and/or 9 areclosed.

The air to be heated is then led through opening 11 in an inversedirection through the installation and can escape through opening 12.

FIG. 2 shows the burner and its surroundings in detail and on anenlarged scale.

FIG. 3 shows a detail of it in a longitudinal section, petpendicular tothat of FIG. 2. This detail show only half, the other half issymmetrical to it. Central conduit 8 for the fuel material connects to acentral hole 16 in block 10.

This block is made of ceramic material the same as the walls of conduits8 and 9 and the walls 1 and 5 of the combustion chamber. The centralhold 16 has a rectangular shape with a ratio of length and width ofapproximately 5:1. in the upper surface 18 of block 10 two rows ofopenings 17 discharge, which are connected with conduit 9. Theseopenings 17 have a rectangular shape, with the short sides of therectangle of the opening aligned head-on, on each row.

Openings 1'7 in each row are placed staggered to the openings of theother row, so that jets of combustion air alternately blow out of theopenings beside each other. This can be obtained when the upper surface18 of the ceramic block is essentially formed by two flat surfacesforming together an angle of about 90.

This shape of the burning block insures an optimal mixture of the fuelmaterial and air, when only the fuel material and the air actuallyescape uniformly out of the sectional area of hole 16 and/or openings17. The latter is obtained by having both conduits 8 and 9 provided witha narrowing down as shown at 19 and 20.

We claim:

1. A ceramic burner, to be used particularly in hot blast stoves forblast furnaces comprising a ceramic block having perforations, avertical conduit for the feeding of gaseous fuel, a second coaxialconduit for the supply of combustion air, said conduits having theirupper ends passing through said perforations, said perforationscomprising a central hole and a crown of holes on each side of thecentral hole, the upper surface of said block slanting upwardly fromsaid central hole and the holes of said crown being directed toward theprolonged axis of said central hole, said central hole havingessentially the shape of a rectangular slot, the sloping part of theupper surface of said block comprising essentially two flat surfaceswhich comprise an angle of 40-l20, and said crown of holes beingsubdivided into two rows of holes running parallel to each other and tothe longitudinal sides of said central hole.

2. A ceramic burner according to claim 1 wherein said two flat surfacescomprise an angle of 60to 90.

3. A burner according to claim 1 wherein the rectangular shape of saidcentral hole shows a ratio of length versus width between 4:1 and 6:1and the slot width is less than 600 mm.

4. Burner according to claim 1 wherein each of said two rows of holeshas at least four holes the middle axis of which form together with theprolongation of the axis of said central hole an angle ranging from 20to 70.

5. Burner according to claim 1 wherein said holes of both rows arealigned on the same height.

6. Burner according to claim 1 wherein said holes of both rows standopposite each other.

7. Burner according to claim ll wherein said holes of one row arestaggered with respect to the other row.

8. Burner according to claim 1 wherein both of said conduits beforepassage to said holes through said ceramic block are narrowed.

9. Burner according to claim 1 wherein both of said rows of holes of thecrown are slot shaped and their greatest dimension is vertically alignedto the longitudinal direction of said central hole.

1. A ceramic burner, to be used particularly in hot blast stoves forblast furnaces comprising a ceramic block having perforations, avertical conduit for the feeding of gaseous fuel, a second coaxialconduit for the supply of combustion air, said conduits having theirupper ends passing through said perforations, said perforationscomprising a central hole and a crown of holes on each side of thecentral hole, the upper surface of said block slanting upwardly fromsaid central hole and the holes of said crown being directed toward theprolonged axis of said central hole, said central hole havingessentially the shape of a rectangular slot, the sloping part of theupper surface of said block comprising essentially two flat surfaceswhich comprise an angle of 40*-120*, and said crown of holes beingsubdivided into two rows of holes running parallel to each other and tothe longitudinal sides of said central hole.
 2. A ceramic burneraccording to claim 1 wherein said two flat surfaces comprise an angle of60*to 90*.
 3. A burner according to claim 1 wherein the rectangularshape of said central hole shows a ratio of length versus width between4:1 and 6:1 and the slot width is less than 600 mm.
 4. Burner accordingto claim 1 wherein eAch of said two rows of holes has at least fourholes the middle axis of which form together with the prolongation ofthe axis of said central hole an angle ranging from 20* to 70*. 5.Burner according to claim 1 wherein said holes of both rows are alignedon the same height.
 6. Burner according to claim 1 wherein said holes ofboth rows stand opposite each other.
 7. Burner according to claim 1wherein said holes of one row are staggered with respect to the otherrow.
 8. Burner according to claim 1 wherein both of said conduits beforepassage to said holes through said ceramic block are narrowed.
 9. Burneraccording to claim 1 wherein both of said rows of holes of the crown areslot shaped and their greatest dimension is vertically aligned to thelongitudinal direction of said central hole.